The decision means CEZ will lose money on the unused fuel from Toshiba Corp’s Westinghouse but the utility said the Russian fuel would boost the output of the reactor, making it more cost efficient, the agency said.

"The unused fuel will certainly be a loss, but on the other hand it will be compensated by being able to increase the output of the reactor," CEZ spokeswoman Eva Novakova said, according to Reuters.

CEZ had considered using both types of fuel temporarily in Temelin’s two reactors but in the end decided that option would be far more complicated than simply not using the fuel bought from Westinghouse.

CEZ said boosting performance of the reactors and reduced downtimes using the Russian fuel would help it meet a goal of raising 2012 production at its two nuclear power plants to 31 terawatt hours from the current 26 terawatt hours, Reuters said.